Winding guide and unwinding
Spinning yarn must be wound onto the drum in a spiral shape. For this purpose, a winding leisure and a yarn guide leisure are required. There are two types of winding: dynamic drum winding and fixed drum winding. The yarn guide is divided into two types: positive yarn arrangement and passive yarn arrangement. The unwinding form can be divided into two types: fixed length type and non-fixed length type. The fixed-length type is suitable for air-jet, water-jet and other jet looms; the non-fixed-length type is suitable for rapier looms and projectile looms.
1. Winding
1. Moving drum winding
As shown in Figure 10-1, the appearance of the moving drum weft feeder and the spinning yarn winding method are shown in Figure 10-1. During winding, the yarn storage drum makes a spiral swing, and the spinning yarn sent out by the tensioner 1 is wound onto the yarn storage drum 2. In order to wind normally, the leading end of the spinning yarn must be held on the rotating drum surface. When unwinding, under the action of the brush ring 3, the spinning yarn only slides along the drum surface, and its tension is relatively uniform. However, the brush ring is subject to strong friction from the spinning yarn and is easily damaged. During operation, pay attention to the coordination of the brush ring and the weft yarn twist direction.
The function of the brush ring is to block the balloon formed when the spinning yarn is unwound, and should not be used to adjust the output tension.
The amount of yarn stored per minute L on the yarn storage drum and the approximate number of yarn windings m’ on the drum are respectively:
L=(1+a)nb
Where: n——the speed of the loom;
a——the coefficient related to factors such as the yarn used for false edges;
b————The reed width of the fabric on the machine;
d————The diameter of the yarn storage drum.
“ Increasing the diameter of the yarn storage drum will increase the rotational inertia of the drum, which is not conducive to starting, braking and high-speed operation; reducing the diameter of the drum will increase the number of yarn winding turns and increase the length of the drum. Usually the diameter of the yarn storage drum is about 130mm.
The structure of the moving drum type weft feeder is complex. The yarn circles on the drum surface are easy to overlap, especially for low-twist yarns. The yarn spacing is small and easy to stick. The yarn storage capacity is limited. It is suitable for situations where the weft insertion rate is less than 1000m/min and Looms with reed width less than 2m.
2. Fixed drum winding
The structure and winding method of the fixed drum weft feeder are shown in Figure 10-2. When winding yarn, the lightweight yarn winding disc 1 rotates and the spinning yarn passes through the yarn guide tube and is wound onto the fixed yarn storage drum 2. The yarn storage drum is looped on the transmission shaft 3, and is fixed to the machine body under the attraction of the permanent magnet 4. When the weft yarn is unwound from the drum surface, uniform tension can be maintained under the action of the tensioner. For devices that use tension rings, when selecting tension rings, pay attention to the direction of the feather or pinnae arrangement, which must match the twist direction of the spinning yarn.
The fixed-drum weft feeder has a simple structure and a large yarn storage capacity. It is suitable for looms with a weft insertion rate of more than 1000m/min and reed widths of more than 2m.
2. Yarn guiding method
Depending on the type of spinning yarn, the requirements for the arrangement of weft yarns are also different. Generally, the requirements for spinning yarns are the same. The yarn storage drum is tightly arranged, but flat yarn and knotted yarn do not agree. It requires the spinning yarn to be arranged at intervals on the yarn storage drum to prevent adhesion of the spinning yarn when unwinding. Due to the above requirements, the yarn guide methods are divided into two types: passive yarn arrangement and positive yarn arrangement.
1. Passive yarn arrangement
When using passive yarn arrangement, there is no special yarn guide mechanism to make the yarn loops neatly and orderly arranged along the axis of the yarn storage drum. The reason why the spinning yarn can slide on the drum surface and form an orderly arrangement depends entirely on the taper and cleanliness of the drum surface, the tension and elasticity of the spinning yarn itself, and the friction coefficient between the spinning yarn and the drum surface. And other factors.
When a cylindrical drum is used, the conical surface at the end of the yarn storage drum can rely on the pushing force formed by the tension of the spinning yarn during rotation to slide the yarn loops along the conical surface into the drum surface one by one. When the angle between the cone surface and the drum surface is α = 135° (Figure 10-1), the yarn loop pushing force is good, so most moving drum type weft feeders adopt this angle. However, this yarn arrangement method easily causes yarn loops to overlap. When a cone drum is used, when the diameter of the yarn circle moves forward along the drum surface, the diameter becomes smaller, and the tension of the spinning yarn decreases accordingly.
2. Positive yarn arrangement
Positive yarn arrangement uses a special yarn arrangement mechanism to push the drum surface of the yarn circle to move. The yarn loops discharged by the yarn arrangement mechanism are divided into two types: compact type and spacing type.
The compact mechanism consists of a transmission shaft, an eccentric bushing and a swash plate. When the transmission shaft rotates, the eccentric inclined sleeve also rotates together, and there is a radial long groove in the swinging swash plate of the looper, and the positioning claw fixed on the yarn storage drum is inserted into the long groove. Since the swinging swash plate is constrained by the inclined sleeve and positioning claws, the swash plate will swing in a wavy manner, pushing the spinning yarn sent from the yarn guide tube in the yarn winding disk to the surface of the yarn storage drum, and actively pushing the yarn Circles to form a regular and tight arrangement on the drum surface. However, spacing type yarn arrangement is required for flat yarns, knotted yarns, etc.
Pitch type yarn arrangement is divided into two types: swing inclined drum type and screw type. The distance between the yarn loops discharged by these two yarn arrangement mechanisms is not adjustable and is generally between 0.8 and 2.1mm.
The swinging inclined drum type yarn arrangement mechanism is widely used, and the Laser/Star type weft feeder produced by Ailuo (Wuxi) Fabric Machinery Co., Ltd. belongs to this type. As shown in Figure 10-3, its transmission principle is similar to the above-mentioned swing swash plate type, but the difference is that a wave-shaped swing drum replaces the wave-shaped swing plate. putThe movable tilting drum and the yarn storage drum are made into grid rod shapes and are nested in each other, with a large gap between the grid rods. Lift the swinging inclined drum upward, take out the yarn hoop from the yarn storage drum, swing forward to make the yarn hoop move along the drum surface, and then swing the tilting drum lower than the yarn storage drum surface and swing back to the starting position. By repeating the above action, the yarn loops will be arranged on the drum surface in a regular and equally spaced form, without overlapping or entanglement, and the yarn spacing can be continuously adjusted.
3. Unwinding
1. Fixed-length unwinding
For jet looms, the yarn is spun through the air flow Or the water pressure drives it to the loom. Since the jet weft insertion length is difficult to determine, the weft feeder needs to limit the number of unwinding yarn turns according to the effective weaving width of the loom. The length fixer (also called the electromagnetic needle) on the weft feeder plays this role. The microprocessor on the jet loom calculates the unwinding time based on the jet flow rate and the preset jet distance, and then controls when the stopper needle of the length fixer is lifted and when it is dropped. The time interval between lifting and falling is Unwinding time. This is the timed fixed-length unwinding. At present, the loop-counting and fixed-length electronic weft feeders are widely used, which can more accurately control the length of the released weft yarn, such as ROJS and Elf electronic weft feeders.
2. Non-fixed length unwinding
Rapier looms and projectile looms, except jet looms, all have weft yarn clamping mechanisms, and the clamping mechanism has a fixed stroke during weft insertion. The weft feeder only needs to be equipped with a tensioner and a damping ring at the unwinding end to provide certain tension and resistance to the unwinding yarn, and the weft feeder can work with the loom. In this way, there is no need for a complicated fixed-length device, which is non-fixed-length unwinding.
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